Spark123, Yes, those, and I would return them and get the right ones if there was somewhere locally to get them.
If the busbar was shortened to not reach the new breaker /could/ the unit be certified with a suitable wire making the final link?
Would the whole system need certification - and if so what extra work would this involve beyond what happens anyway for a circuit certification?
>Ze and resultant PSSC is at the CU
Some of these acronyms even the internet doesn't know how to decipher
Z I assume is impedance, Ze - earth impedance?
PSSC I am having trouble with
>so this alone will probably tell you what could happen if something goes wrong.
Logically this is behind the RCD, so any leak to earth is as protected as any socket in the house.
So "the only" thing I have to worry about is the load on the cable/bus bar causing a fire.
The bus bar is symmetrical - i.e. the RCD feeds the busbar through /exactly/ the same size connectors as those that feed each MCB. This must mean that each connection on the busbar is rated for 80A (as is the upstream RCD).
To follow through with this thinking, a single link from the new MCB to the busbar (on any connection) should only /need/ to be able to carry the rated load of the breaker - in this case 32A, which should be good on 6mm over this distance.
If more current makes it through the MCB than it is rated for then all bets are off, but that is standard everywhere in the system!
Also, if someone loops back out of the MCB to another new MCB then the connecting wire must be able to handle the combined load. But this isn't whet is being suggested, there is no space for more breakers, and I can't really plan for what someone unknown in the future might do!
>What was wrong with the original 32amp MCB?
It didn't exist
"Originally" it would seem that the CU was set up in the following way
Isolator
->Upstairs lights
->Downstairs lights
->RCD (80A)
--->Shower (32A) 6mm radial
--->Sockets, house and kitchen (32A) ~2mm ring
--->Sockets + boiler, (16A) Utility room ~2mm radial
--->Cooker, (32A) 6mm radial
by the time we moved in
Isolator
->Upstairs lights
->Downstairs lights
->RCD (80A)
--->Shower (32A) 6mm radial
--->Sockets, house and kitchen (32A) ~2mm ring
--->Sockets + boiler, (16A) Utility room, outside lying in flowerbed, twin 13A sockets ~2mm radial
--->Under floor hearing for conservatory , (32A) 2.5mm radial surface trunked
no connection to cooker which is gas - plugged into house ring.
What I have done is:
Rewired the utility in 4mm ring, using the 32A breaker from the underfloor heating. This ring need to be 32A as it has the washing machine and dishwasher on the circuit and that overpowers the 16A trip
Added a new ring for the kitchen in 4mm, putting the underfloor heating onto this circuit. Realistically the underfloor heating + kettle are the only big items on this circuit.
Added a new radial for the cooker in 6mm (I am replacing the cooker with a gas hob + electric oven, so there is only really going to be ~13Amp on this circuit - but might as well make the most of the opportunity to fit heavy gauge wire should we want to fit an electric hob in the future)
So I am planning on removing the 16Amp trip and replacing it with a new 32A for the new ring, plus, adding a new 32A trip for the new radial into the empty slot in the MCB
